Although applicable in numerous applications for analyzing surfaces of a wide range of structures and various materials, the present disclosure and the problems on which it is based are described in greater detail in relation to surface analysis of fiber composite plastics material aircraft structures.
For the industrial manufacture of molded components from fiber-reinforced plastics material (FRP), in particular carbon-fiber-reinforced plastics material (CFRP), molding tools are often used, in which the components are shaped. For this purpose, for example, a fiber material semi-finished product, for example mats made of unidirectional carbon fiber layers, can be impregnated with a matrix material, for example epoxy resin, and cured in the molding tool by applying pressure and temperature. The mold surface of the molding tool determines the surface contour of the finished component which is left behind after curing. Molding tools of this type are often coated with a release agent before use (for example by applying a liquid chemical release agent) so as to be able to release the finished components from the molding tool as easily as possible. After the component is demolded, depending on the method of manufacture, undesired release agent residues may be left behind both on the mold surface and on the component.
Generally, it is desirable to form and obtain FRP components having as precisely defined and clean a surface as possible, so as to provide for further use or machining. Thus, for example, the adhesive properties of a component can be influenced if the surface thereof is soiled or contaminated with undesired substances. Furthermore, good adhesion properties are advantageous for painting or coating a component. Accordingly, there is a need for methods which qualitatively and quantitatively detect impurities on surfaces of FRP components.
For example, laser-induced plasma spectroscopy makes it possible to detect the chemical element silicon in surface contaminations consisting of siloxanes. As a further example, U.S. Pat. No. 8,330,109 B2 teaches that FTIR spectroscopy (“Fourier transform infrared spectrometer”) can be used for detecting surface impurities on non-metal materials. DE 10 2011 102 055 B4 further discloses a method in which a fiber composite component is heated regionally to desorb contaminant substances which are thereupon detected as gas by a plurality of sensors. Generally, in similar methods, sample surfaces can be heated using various forms of radiation so as to convert non-volatile substances into gas at least in part and subsequently to detect them using a detector. Furthermore, for example, U.S. Pat. No. 8,064,570 B2 discloses handheld analysis instruments for X-ray fluorescence analysis (XRFA), by which elements in substance samples can be detected.